Editing Spring Triangle

{{Short description|Pattern of stars in the Northern Hemisphere}}
[[File:Spring Triangle (Stellarium).png|thumb|The Spring Triangle with [[Arcturus]], [[Spica]], [[Regulus]], and [[Denebola]]|upright=1.4]]
The '''Spring Triangle''' is an [[asterism_(astronomy)|astronomical asterism]] involving an imaginary triangle drawn upon the [[celestial sphere]], with its defining vertices at [[Arcturus]], [[Spica]], and [[Regulus]].<ref name=":2">{{Cite web |title=Spring Triangle – Constellation Guide |url=https://www.constellation-guide.com/spring-triangle/ |access-date=2023-03-21 |website=www.constellation-guide.com}}</ref> This triangle connects the [[constellation]]s of [[Boötes]], [[Virgo (constellation)|Virgo]], and [[Leo (constellation)|Leo]]. It is visible in the evening rising in the southeastern sky of the [[northern hemisphere|Northern Hemisphere]] between March and May and setting until August, while at morning rising and setting from November to the end of February.

[[George Lovi]] of [[Sky & Telescope]] magazine had a slightly different Spring Triangle, including the tail of Leo, with [[Denebola]] replacing [[Regulus]]. Although Denebola is dimmer, this triangle is more nearly equilateral.<ref>{{cite web |title=How to See Mars and Saturn in Night Sky's Spring Triangle |date=2012-06-11 |website=[[Space.com]] |archive-url=https://web.archive.org/web/20230529185448/https://www.space.com/16085-spring-triangle-stars-skywatching.html |archive-date=2023-05-29 |url-status=live |url=http://www.space.com/16085-spring-triangle-stars-skywatching.html}}</ref>  These stars, together with [[Cor Caroli]], form parts of a larger spring asterism called the [[Great Diamond]].

==The stars of the Spring Triangle==
{| class="wikitable"
!Constellation
!Name
![[Apparent magnitude]]<ref name=":1">{{Cite web |title=Brightest Stars |url=http://stars.astro.illinois.edu/sow/bright.html |access-date=2023-04-16 |website=stars.astro.illinois.edu}}</ref>
![[Luminosity]]<ref name=":1" /><br/>({{solar luminosity|link=y}})
![[Stellar classification|Spectral type]]<ref name=":1" />
!Distance<ref name=":1" /><br/>([[light year]]s)
|- align=center
![[Boötes]]||[[Arcturus]]
||−0.04||103.75 ||K1.5III||37
|- align=center
![[Virgo (constellation)|Virgo]]||[[Spica]]
||1.04||1770||B1V + B4V||250
|- align=center
!rowspan=2|[[Leo (constellation)|Leo]]||[[Regulus]]
||1.35||134.28||B7V||79
|- align=center
![[Denebola]]
||2.14||13.43||A3V||36
|}

=== Arcturus (α Boötes) ===
Arcturus is a giant orange star in the constellation [[Boötes]]. Located only 37 light years away,<ref>{{Cite web |date=2022-05-18 |title=EarthSky {{!}} Arcturus, brightest star of the north |url=https://earthsky.org/brightest-stars/bright-orange-arcturus-use-the-big-dipper-to-find-it/ |access-date=2023-02-25 |website=earthsky.org |language=en-US}}</ref> it has an apparent magnitude of -0.04.<ref>{{Cite journal |last=Ducati |first=J. R. |date=2002-01-01 |title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system. |url=https://ui.adsabs.harvard.edu/abs/2002yCat.2237....0D |journal=VizieR Online Data Catalog|volume=2237 |bibcode=2002yCat.2237....0D }}</ref> It is the brightest star in the Northern Hemisphere and fourth brightest in the night sky.<ref>{{Cite web |title=Spring Triangle Asterism: Stars, Location, Features & More |url=https://theplanets.org/asterisms/spring-triangle-asterism/ |access-date=2023-02-25 |website=The Planets |language=en-US}}</ref>
[[File:Boötes constellation map.svg|thumb|upright|[[Arcturus]] found in the constellation [[Boötes]]|left]]
Because it is spotted easily, Arcturus was identified by ancient humans and tied to mythological ideals. The star was given its name from the [[ancient Greek]] Ἀρκτοῦρος (''Arktouros''), which translates to "Guardian of the Bear."<ref>{{Cite journal |last1=Ramya |first1=P. |last2=Reddy |first2=Bacham E. |last3=Lambert |first3=David L. |date=2012-09-05 |title=Chemical compositions of stars in two stellar streams from the Galactic thick disc |journal=Monthly Notices of the Royal Astronomical Society |volume=425 |issue=4 |pages=3188–3200 |doi=10.1111/j.1365-2966.2012.21677.x |doi-access=free |arxiv=1207.0767 |bibcode=2012MNRAS.425.3188R |s2cid=119253279 |issn=0035-8711}}</ref> This name was selected because of the star's proximity to [[Ursa Major]] and [[Ursa Minor]], surmising the two bear constellations were guarded by Arcturus.<ref>{{Cite web |last=Ian |date=2020-01-20 |title=Arcturus (α Boötis) {{!}} Facts, Information, History & Definition |url=https://nineplanets.org/arcturus-α-bootis/ |access-date=2023-02-25 |website=The Nine Planets |language=en-US}}</ref>

Arcturus is thought to be around 6 to 8.5 billion years old,<ref>{{Cite journal |last1=Ramírez |first1=I. |last2=Allende Prieto |first2=C. |date=2011-12-01 |title=Fundamental Parameters and Chemical Composition of Arcturus |url=https://ui.adsabs.harvard.edu/abs/2011ApJ...743..135R |journal=The Astrophysical Journal |volume=743 |issue=2 |pages=135 |doi=10.1088/0004-637X/743/2/135 |arxiv=1109.4425 |bibcode=2011ApJ...743..135R |s2cid=119186472 |issn=0004-637X}}</ref> and has traveled up the red-giant branch of the [[Hertzsprung–Russell diagram|Hertzsprung-Russell diagram]] as it has expanded in size. The star has a diameter of around 36 million km, making it about 26 times larger than the [[Sun]].<ref>{{Cite web |last=Ian |date=2020-01-20 |title=Arcturus (α Boötis) {{!}} Facts, Information, History & Definition |url=https://nineplanets.org/arcturus-α-bootis/ |access-date=2023-02-25 |website=The Nine Planets |language=en-US}}</ref> Despite this size difference, the mass of Arcturus is only 1.1 times that of the Sun. 

With its high speed of 122 km/s (270,000 mph) and a path which crosses the [[galactic plane]] rather than residing within it, Arcturus may have formed outside of the [[Milky Way]].<ref>{{Cite journal |last1=Ramya |first1=P. |last2=Reddy |first2=Bacham E. |last3=Lambert |first3=David L. |date=2012-09-05 |title=Chemical compositions of stars in two stellar streams from the Galactic thick disc |journal=Monthly Notices of the Royal Astronomical Society |volume=425 |issue=4 |pages=3188–3200 |doi=10.1111/j.1365-2966.2012.21677.x |doi-access=free |arxiv=1207.0767 |bibcode=2012MNRAS.425.3188R |s2cid=119253279 |issn=0035-8711}}</ref> The star is the namesake of a group of 52 other stars named the [[Arcturus moving group]] or Arcturus stream, all of which share a similar [[proper motion]]. It has been proposed that these stars are remnants of an ancient dwarf [[satellite galaxy]] that was assimilated into the Milky Way long ago.<ref>{{Cite journal |last1=Ibata |first1=Rodrigo |last2=Gibson |first2=Brad |date=April 2007 |title=The Ghosts of Galaxies Past |url=http://dx.doi.org/10.1038/scientificamerican0407-40 |journal=Scientific American |volume=296 |issue=4 |pages=40–45 |doi=10.1038/scientificamerican0407-40 |pmid=17479629 |bibcode=2007SciAm.296d..40I |issn=0036-8733|url-access=subscription }}</ref> 

=== Spica (α Virginis) ===
Spica is a [[Binary star|binary]] blue-white star pair that appears as a single point of light from Earth, and is commonly if incorrectly referred to as a single star. The star system is 250 light years away and has an apparent magnitude of 1.04.<ref>{{Cite web |date=2021-07-15 |title=EarthSky {{!}} Spica, bright beacon of Virgo, is 2 stars |url=https://earthsky.org/brightest-stars/speed-on-to-spica-the-15th-brightest-star/ |access-date=2023-03-10 |website=earthsky.org |language=en-US}}</ref> It is the brightest star in the [[Virgo (constellation)|constellation Virgo]], and is the 15th brightest star in the night sky.<ref name=":0">{{Cite web |title=Brightest Stars |url=https://web.pa.msu.edu/people/horvatin/Astronomy_Facts/brightest_stars.html |access-date=2023-03-10 |website=web.pa.msu.edu}}</ref> The name Spica is derived from a Latin phrase that describes the [[zodiac]] sign [[Virgo (astrology)|Virgo]] as holding an ear of grain, ''spīca virginis.''<ref>{{Cite web |author1=Elizabeth Howell |date=2013-07-20 |title=Spica: The Close Binary |url=https://www.space.com/22049-spica.html |access-date=2023-03-10 |website=Space.com |language=en}}</ref> Virgo the Maiden is often represented as a young woman holding this stalk of grain. 

The best times of the year to view this star are during early spring to late summer in the Northern Hemisphere. To find this star easily, locate the Big Dipper and follow the curve of its handle. This curve will first lead to [[Arcturus]]. Finally, "drive a spike" directly to Spica.<ref>{{Cite web |date=2017-04-01 |title=Extend Big Dipper's handle to Spica {{!}} Sky Archive {{!}} EarthSky |url=https://earthsky.org/tonight/drive-a-spike-to-spica/ |access-date=2023-03-10 |website=earthsky.org |language=en-US}}</ref>[[File:Virgo constellation map.png|thumb|The constellation of [[Virgo (constellation)|Virgo]]]]
Spica is made up of two individual stars, Spica A and Spica B, with radii of 7.40 and 3.64 times the Sun's, respectively.<ref>{{Cite web |title=Spica Star - Features & Facts About Alpha Virginis |url=https://theplanets.org/stars/spica-star/ |access-date=2023-03-10 |website=The Planets |language=en-US}}</ref> Their sizes contribute greatly to the brightness of the stars. Spica A's luminosity is 12,100 times that of the Sun, while Spica B has a luminosity of 1,500.<ref>{{Cite web |title=Spica - Alpha Virginis |url=http://astropixels.com/stars/Spica-01.html#:~:text=Spica%20has%20a%20spectral%20type,diameter%207.4%20times%20the%20Sun. |access-date=2023-03-10 |website=astropixels.com}}</ref> Their sizes lead to respective surface temperatures of 22,400 K and 18,500 K, much higher than the Sun. They are separated by a distance of only 0.12 [[Astronomical unit|AU]] with an orbital period of only four days. This proximity gravitationally distorts each star into an egg shape, with the pointed ends facing each other.<ref>{{Cite web |last=Ian |date=2020-01-20 |title=Spica (α Virginis) {{!}} Facts, Information, History & Definition |url=https://nineplanets.org/spica-α-virginis/ |access-date=2023-03-10 |website=The Nine Planets |language=en-US}}</ref>

=== Regulus (α Leonis) ===
[[File:Regulus star system.png|thumb|A look at the four star system of [[Regulus]]|left]]
Regulus, the brightest object in the constellation [[Leo (constellation)|Leo]], is a quadruple star system made up of two separate pairs of stars.<ref>{{Cite web |last=Ian |date=2020-01-20 |title=Regulus (α Leonis) {{!}} Facts, Information, History & Definition |url=https://nineplanets.org/regulus-α-leonis/ |access-date=2023-03-21 |website=The Nine Planets |language=en-US}}</ref> At 79 light years away and an apparent magnitude of 1.35, Regulus is the 21st brightest star in the sky.<ref name=":0" /> The name Regulus, which translates to "little king" in Latin, was given to the system by Polish astronomer [[Nicolaus Copernicus]] in the 16th century.<ref>{{Cite web |author1=Elizabeth Howell |date=2013-09-21 |title=Regulus: The Kingly Star |url=https://www.space.com/22890-regulus.html |access-date=2023-03-21 |website=Space.com |language=en}}</ref> The star can be seen at the base of the head of Leo that looks like a backwards question mark, which is also referred to as [[the sickle|the Sickle]]. 

The brighter pair of stars is called Regulus A, which is made up of a large visible bright blue star and its companion, Regulus D, which is possibly a white dwarf, though this is unconfirmed. This smaller companion has a mass of only 0.3 solar masses, while the mass of the larger is 3.8 solar masses. The pair are close at 0.35 AU apart, with a short orbital period of 40.11 days around a center mass.<ref>{{Cite web |date=2022-05-06 |title=EarthSky {{!}} Meet Regulus, the Lion's Heart |url=https://earthsky.org/brightest-stars/best-regulus-the-heart-of-the-lion/ |access-date=2023-03-21 |website=earthsky.org |language=en-US}}</ref> The other two stars are the main sequence orange dwarf Regulus B and its red dwarf companion Regulus C. With apparent magnitudes of 8.13 and 13.50, they can't be seen with naked eye.<ref>{{Cite web |title=Regulus Star - Facts & Features About The Little King |url=https://theplanets.org/stars/regulus-star/ |access-date=2023-03-21 |website=The Planets |language=en-US}}</ref> This means the entire system is named after its brightest star. 

Regulus A appears egg-shaped due to an extreme rotational speed. While the Sun rotates on its axis once every 27 days at a speed of 7,242 kph (4,500 mph), Regulus rotates every 16 hours at 1.1 million kph (700,000 mph). Astronomers have determined that if the star rotated 10% faster it would rip itself apart.<ref>{{Cite web |author1=Tariq Malik |date=2005-01-31 |title=Leo's Bright Star Regulus Flies like Bullet |url=https://www.space.com/736-leo-bright-star-regulus-flies-bullet.html |access-date=2023-04-02 |website=Space.com |language=en}}</ref>

=== Denebola (β Leonis) ===
[[File:Leo constellation map.png|thumb|Positions of stars [[Denebola]] and [[Regulus]] in [[Leo (constellation)|Leo]]]]
Denebola is a white main sequence star in the constellation Leo. With a distance of 36 light years from Earth, and an apparent magnitude of 2.14,<ref>{{Cite web |last=admin |date=2020-04-27 |title=Denebola (Beta Leonis): Star Type, Facts, Name, Location, Constellation {{!}} Star Facts |url=https://www.star-facts.com/denebola/ |access-date=2023-04-16 |language=en-US}}</ref> it is the third brightest star in the constellation and the 62nd in the night sky.<ref name=":0" /> This star has often taken the place of Regulus in the Spring Triangle. While Regulus has a higher magnitude, Denebola makes the triangle more equilateral in appearance. 

The star's name comes from the Arabic phrase Deneb Elased, or ðanab al-asad, meaning "the tail of the lion."<ref>{{Cite web |last=Jamie |date=2015-08-04 |title=Fixed Star Denebola |url=https://astrologyking.com/denebola-star/ |access-date=2023-04-16 |website=Astrology King |language=en-US}}</ref> This refers to the star's position in the constellation at the lion's tail end. Denebola has a mass of 1.78 solar masses and a radius of 1.728 solar radii, making it almost twice the size of our sun. It may be a Delta Scuti type variable star due to its variations in brightness; about 10 times a day the star's brightness fluctuates in magnitudes around 0.025.<ref>{{Cite web |last=Ian |date=2020-02-04 |title=Denebola (β Leonis) {{!}} Facts, Information, History & Definition |url=https://nineplanets.org/denebola-β-leonis/ |access-date=2023-04-16 |website=The Nine Planets |language=en-US}}</ref>

== Deep Sky Objects ==
[[File:The Great Virgo Cluster.png|thumb|The [[Virgo Cluster]]]]
The Spring Triangle contains multiple objects of note, with a large amount of them belonging to the [[Virgo Cluster]]. This cluster contains around 1,500 galaxies and can be seen between the stars Denebola and Vindemiatrix, with many being notable Messier objects.<ref name=":2" />

=== Messier 87 ===
[[File:Black hole - Messier 87.jpg|thumb|left|Supermassive black hole at the center of [[Messier 87|M87]]]]
The brightest galaxy seen in the cluster is the supergiant elliptical galaxy [[Messier 87]]. With an apparent magnitude of 9.6, the galaxy can be seen using a telescope, as it was first seen by [[Charles Messier]] in 1781. Located 54 million light years away and at 130,000 light years across, M87 houses several trillions of stars and around 15,000 [[Globular cluster|globular star clusters]].<ref>{{Cite web |title=Messier 87 - M87 - Elliptical Galaxy {{!}} freestarcharts.com |url=https://freestarcharts.com/messier-87 |access-date=2023-04-19 |website=freestarcharts.com}}</ref> For comparison, the Milky Way is 105,700 light years across and contains around 200 billion stars.<ref>{{Cite web |title=ChView - THE STARS OF THE MILKY WAY |url=http://members.nova.org/~sol/chview/chv5.htm |access-date=2023-04-19 |website=members.nova.org}}</ref>

At the center of this galaxy there is a [[supermassive black hole]] (of 6.5 billion solar masses) bearing a large blue [[Astrophysical jet|jet]] of subatomic particles accelerated to speeds close to the speed of light.<ref>{{Cite web |last=Garner |first=Rob |date=2017-10-06 |title=Messier 87 |url=http://www.nasa.gov/feature/goddard/2017/messier-87 |access-date=2023-04-19 |website=NASA}}</ref> In 2019, an image of this black hole, designated M87*,<ref>{{Cite web |title=The Astrophysical Journal Letters - IOPscience |url=https://iopscience.iop.org/journal/2041-8205 |access-date=2023-04-19 |website=iopscience.iop.org |language=en}}</ref> was published by the [[Event Horizon Telescope|Event Horizon Telescope collaboration]] -- the first picture of a black hole ever released.<ref>{{Cite journal |last=Castelvecchi |first=Davide |date=2020-09-23 |title=The first-ever image of a black hole is now a movie |url=https://www.nature.com/articles/d41586-020-02717-3 |journal=Nature |language=en |volume=586 |issue=7827 |pages=18–19 |doi=10.1038/d41586-020-02717-3|pmid=32968248 |bibcode=2020Natur.586...18C |s2cid=221888158 |url-access=subscription }}</ref>

=== Messier 49 ===
[[Messier 49]] is the brightest galaxy in the Virgo group with an apparent magnitude of 9.4. This brightness allowed M49 to be the first observed in the group, by [[Nicolas-Louis de Lacaille|Nicolas Louis de Lacaille]] in 1752. The giant [[elliptical galaxy]] is located 56 million light years from Earth, and is around 157,000 light years across, with more than 200 billion stars.<ref>{{Cite web |last=admin |date=2015-05-29 |title=Messier 49 |url=https://www.messier-objects.com/messier-49/ |access-date=2023-04-21 |website=Messier Objects |language=en-US}}</ref> 

=== Siamese Twins Galaxies (NGC 4567 and NGC 4568) ===
[[File:NGC 4567 & 4568.png|thumb|[[NGC 4567 and NGC 4568]]]]
Also known as the [[NGC 4567 and NGC 4568|Butterfly Galaxies]], NGC 4567 and 4586 are two [[Barred spiral galaxy|unbarred spiral galaxies]] that are colliding. The pair were first discovered by astronomer [[William Herschel]] in 1784, but did not earn their name until observer [[Ralph Copeland]] called them the Siamese Twins in the late 1800s due to their almost identical shape and structure.<ref>{{Cite web |title=Webb Deep-Sky Society: Observations of NGC4567 |url=https://www.webbdeepsky.com/observations/object?object=NGC4567 |access-date=2023-04-21 |website=www.webbdeepsky.com}}</ref> The galaxies are located around 52 million light years away, with a separation between the cores of around 20,000 light years.<ref>{{Cite web |title=Twin Galaxies in Virgo {{!}} Science Mission Directorate |url=https://science.nasa.gov/twin-galaxies-virgo |access-date=2023-04-21 |website=science.nasa.gov}}</ref> The more distant galaxy, NGC 4567, has an apparent magnitude of 11.5 and is oriented almost completely face-on with our galaxy. The closer galaxy, NGC 4568, has an apparent magnitude of 11.2 and is oriented at a diagonal. It was originally believed that the two were simply passing directly behind each other in the same line of sight, but further observations and studies have observed a high rate of star formation where the galaxies overlap, confirming that they are undergoing the early phases of collision and merging.<ref>{{Cite web |title=Siamese Twins Galaxies: NGC 4567 and NGC 4568 – Constellation Guide |url=https://www.constellation-guide.com/siamese-twins-galaxies/ |access-date=2023-04-21 |website=www.constellation-guide.com}}</ref>

=== Other Objects ===
There are many other notable members in the triangle, including [[Messier 60]], [[Messier 84]], and [[Messier 86]]. Two named groups of galaxies are the [[Eyes Galaxies]] (NGC 4435 and NGC 4438) and the [[Leo Triplet]] ([[NGC 3628]], [[Messier 65]], [[Messier 66]]).<ref name=":2" />

==See also==
*[[Summer Triangle]]
*[[Winter Triangle]]
*[[Northern Cross (asterism)|Northern Cross]]

== References ==
{{reflist}}

== External links ==
* [http://starryskies.com/articles/dln/4-99/leo.html Lions in the Sky and other Spring Treasures] 
* [http://www.space.com/3909-spring-triangle.html The Spring Triangle] Shows [[Denebola]] instead of [[Regulus]] in the spring triangle

[[Category:Asterisms (astronomy)]]
[[Category:Leo (constellation)]]
[[Category:Virgo (constellation)]]
[[Category:Boötes]]